Calorimetric Biosensing System for Quantification of Urinary Creatinine

Area of Science:

• Analytical Chemistry
• Biomedical Engineering
• Materials Science

Background:

• Accurate quantification of creatinine in human urine is crucial for diagnosing kidney function and other health conditions.
• Existing methods for creatinine measurement can be complex or lack robustness.
• Microcalorimetric sensing offers a sensitive and potentially portable approach for biomarker detection.

Purpose of the Study:

• To develop and validate a microcalorimetric sensing system for the precise quantification of creatinine in human urine samples.
• To demonstrate the robustness and sensitivity of a novel sensor design decoupling analyte fluidics from quartz resonators.
• To compare the performance of the microcalorimetric system with established High-Performance Liquid Chromatography (HPLC) methods.

Main Methods:

• Fabrication of a microcalorimetric sensor array using microfabricated Y-cut quartz resonators (10 μm thickness, 166 MHz resonance).
• Utilizing the high temperature sensitivity of quartz resonators (14,600 Hz/K) for calorimetric detection.
• Employing alginate-entrapped creatinine deiminase for enzymatic transduction of creatinine into measurable temperature signatures.
• Decoupling sensor elements from fluidics and using focused ion beam etching for thermal isolation of a reference resonator.

Main Results:

• The microcalorimetric system successfully quantified creatinine in human urine samples.
• A decoupled sensor design enhanced system robustness compared to directly contacted calorimeters.
• The sensor exhibited high temperature sensitivity due to the properties of high-frequency quartz.
• Calorimetric measurements showed good agreement with results obtained using traditional HPLC methods for 5 urine samples.

Conclusions:

• The developed microcalorimetric sensing system provides a robust and sensitive platform for human urinary creatinine quantification.
• The decoupled sensor architecture is a key innovation for improved calorimetric system stability.
• This approach shows promise as a viable alternative to conventional methods for creatinine analysis, potentially enabling more accessible diagnostics.